New paradigm for ultrahigh electro-optic activity: through supramolecular self-assembly and novel lattice hardening

A major breakthrough in the area of organic electro-optic (EO) materials has been recently achieved. To go beyond the oriented gas model limit for organic EO materials, new approaches of using nanoscale architecture control and supramolecular self-assembly have been proved as a very effective method to create a new paradigm for materials with very exciting properties. High-performance EO polymers were demonstrated by a facile and reliable Diels-Alder "click" reaction for postfunctionalization and lattice hardening to improve EO activity and thermal stability. This type of "click" chemistry paves the way to systematically study the relationship among EO activity, chromophore shape, and number density of the chromophores. Reversible supramolecular interactions were also introduced to a new generation of EO dendrimers and polymers to create self-assembled nano-objects, overcome strong intermolecular electrostatic interaction, and improve their poling efficiency and stability. These self-organized EO materials were used as hosts in a binary chromophore system to further improve chromophore number density and r₃₃ value. With these novel approaches, we succeeded in enlarging the full potential of organic NLO materials by a factor of 3∼5 and developing a variety of nano-structured organic EO materials with ultrahigh r₃₃ values (>300 pm/V at the wavelengths of 1310 and 1550 nm, more than 10 times that of LiNbO₃) and excellent auxiliary property, such as thermal stability and optical transparency. The success of these material developments has inspired the exploration of new device concepts to take full advantage of organic EO materials with ultrahigh r₃₃ values.